Method of making surfacing materials



Patented Sept. 6, 1932 UNITED STATES PATENTIoFFiCE TION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE METHOD OF MAKING SURFACING MATERIALS No Drawing.

This invention relates to an improved method of making surfacing materials, such as are adapted for use in surfacing roadways, sidewalks, and the like, and more particularly to that class of surfacing materials which comprise a mineral aggregate in combination with a bituminous or asphaltic binder material.

In the formation of paving and surfacing materials of this character it has been the practice in the art to form such materials by what is commonly termed the Fhot mix method, that is, by combining the mineral aggregate with a bituminous or asphaltic binder by mixing the components at a relatively high I temperature, .such as from 27 5 degrees to 425 degrees F. In forming a surfacingmaterial in this manner, however, certain of the lighter petroleum constituents initially present in the bituminous or asphaltic binder material .1 are not completely removed and other components of the binder material are affected by the high temperatures in sucha manner that they lose their natural binding power to a considerable degree so that the resulting material is lacking in wearing qualities and prone to early deterioration. The present invention'is designed to produce a surfacing material closely approximating certain of the natural rock asphalts in its composition and inherent characteristics, and to form the same in a relatively simply and inexpensive manner without subjecting the binder constituent of the material to such a high temperature as will cause early deterioration thereof.-

One object of the invention, therefore, is to provide a method for forming a bituminous surfacing material which contains a hard mineral aggregate in such a manner that the physical characteristics of the resulting material will closely approximate or be substantially the same as those of the natural rock asphalts.

A further object of the invention is to pro vide an improved process for forming a bituminous surfacing material by treating a bi- Application filed March 10, 1930. Serial No. 434,818.

Another object of the invention is to pro-- vide an improved process for forming a bituminous surfacing material by treating the bituminous or asphaltic content thereof to remove or substantially removethe lighterand more volatile petroleum constituents prior to the mixing of the same with the mineral aggregate and to effect this removal without-subj ecting the bituminous to undue heat. r i

A further object of the inventionis to provide .an improved process for forming a bituminous surfacing material comprising a bituminous binder material combined with a mineralaggregate in such a manner that the heavier lubricating constituents of the petroleum content may be retained therein without or asphaltic material JOHN w. CLARK, on NEW YORK, N. Y., ASSiGNOR T nnusnnenn CHEMICAL conronm impairment of their preservative qualities and the lighter andmore volatile constituents removed prior to the mixing of the bituminous binder material with the mineral aggregate.

Another object of the invention is to effect the combination of the bituminousjma terial and mineral aggregate in such a manner that the operation may be carried out in an open chamber, and ata relatively low temperature whereby a thorough mixing of the constituents may be effected without injury to the bituminous material.

Other objects. and advantagesof the invention relate to various improved steps and combination of steps in the carrying-out of the process as will be more fully set forth in the detailed description to follow.

In carrying out the improved process it is proposed to employ .a bituminous matter which comprises bitumen or asphalt,,com-.

asphaltic base and from which the greater.

part of the more volatile-elementshave been removed by distillation. The term bitumen as used herein is employed to designate a natural asphalt or a petroleum residue from which both the light and heavy oils have vbeen substantially completely removed, or

any suitable mixture of these materials while the term bituminous binder or bituminous binder material as used herein designates the product obtained by incorporating in such bitumen a sufficient amount of crude petroleum or'heavy oils having. an asphaltic base as to insure a proper mixture of the bitumen and heavy ethereal oils for impartingthe desired degree ofpliability to the bituminous binder and preventing its early deterioration through loss of those heavy oils which are present therein in its natural state.

This bituminous binder material may be prepared from a natural asphalt or from bi-, tumen or both by adding thereto a crude petroleum from which the volatile elements have been removedby topping or by add ing thereto heavy petroleum oils having an asphaltic base. By heavy petroleum oils is meant those heavy, low boiling point hydrocarbon oils which remain after the petroleum has been subjectedto fractional distillation to remove its more volatile constituents.

The bituminous binder material'may be a petroleum residue having an asph'altic base and which contains at least of asphalt and 25% of petroleum oils, such, for exam-- ple as Penuca oil. Whether the bituminous binder material is prepared byadding' crude petroleum orheavy oils to asphaltor bitu- 'men or both,'or whether a residue containfluidity and serve as a lubricating agent and preservative for the bitumen so that the bituminous binder material when combined with themineral aggregate will possess the necessary plasticity to permit the finished materials to be readily handled and spread as well as to prevent early deterioration of the final material such aswould result if asphalt orbitumen uncombined with the heavier hydrocarbon oils was employed.

The heavier petroleum oils as added to the asphalt 1n the form of crude petroleum or as present in the Penuca oil also acts as'a partial solvent for the asphalt to effect a quick and complete coating of each mineral ticle with the bituminous binder material. This bituminous binder as it is present in the completedproduct should not contain any substantial proportion of thelighter volatile hydrocarbons, such as gasolene, benzene, and the like, as the presence of these lighter hydrocarbons will tend to render the bitum'n nous binder material unduly soft, thus causing the final product to congeal unduly, and their presence would result in breaking down the coating which the bituminous binder material is intended to form around each mineral particle. I

By the addition to the asphalt or bitumen of the heavier petroleum oils or ethereal oils as above described there is incorporated in the bitumen a certain proportion of those heavy oils of the same or similar character to those heavyoils which are removed from the bitumen in the final stages of its separation from petroleum. These oils serve the double purpose of rendering the bitumen more fluid foruse at relatively low temperatures in coating the mineral particles and also act lubricants or preservatives to-prolong the life qualities of the bitumen content of the finished material. 7

While the main portion or bulk of the lighter and more volatile hydrocarbons, such as, gasoline, benzene and the like, have been removed from the crude petroleum oils or petr leum residues which are used in forming thebituminous binder, a small proportion of these lighter and more volatile constituents is contained in the crude petroleum or petroleum residue which must be substantially en- 7 tirely removed either directly from the crude petroleum or petroleum residues prior to their incorporation with the asphalt or bitumen or after such mixture has been effected in order to prevent deterioration'of the paving material throughthe injurious action caused by the presence of the volatile hydrocarbons.

If the mineral aggregate is to'be-coated at relatively low temperatures, as is desirable to prevent injury to the bitumen content of the material, a somewhat larger proportion of heavy oils should be employed than would be required in carrying out the mixing operation at higher temperatures, and larger proportions of the oils may be required if the oils contain a considerable quantity of the lighter hydrocarbons which are to be driven off in heating the combined material in vacuo. In general it is regarded as preferable that the heavy oils added to or present in combination with the bitumen be equal to from 8% to 25% of the bitumen by weight, although I am aware that these limits may be varied in some cases, and consequently set them forth herein for the purpose of illustration rather than as absolute limitations to be strictly followed in all cases.

The mineral aggregate which is to be incorporated in the bituminous binder material may vary somewhat dependent upon theuse for which it is to be employed. Preferably the mineral aggregate is ahard silicious or a stone material, free from lime or limestone,

and it may be sand, crushed rock, or sand-.

unduly hard and brittle. When the mate rial is to be used as a surfacing for roads and the like, the mineral aggregateis preferably formed from fine, hard,-sharp, silicia sand which may be of such size as to pass through a sieve of from 10 to i 200 mesh to the inch. l/Vhen the final material is to be employed as sub-surfacing for roadways and the like, a part or all of the mineral particles may be from to inch in diameter, and this coarser aggregate may be used alone or may be mixed with a more finely divided mineral material, such, for example, as the fine sand previously described. In either case it is preferred that the mineral matter be in the form of hard, sharp sand or stone particles which will not break or fracture under the weight of heavy loads and which may be thoroughly coated with the bituminous binder material.

It has previously been proposed to combine the bituminous binder material and mineral aggregates by adding a solvent liquid, such as benzol, to the bituminous binder, then adding the mineral aggregate, which is thoroughly incorporated into the mass by mixing, and subjecting the combined material to heat while under vacuum to remove thebenzol-solvent, any moisture present in the mineral aggregate, and such of the lighter and more volatile hydrocarbons as are present in the crude petroleum'or petroleum residues employed in forming the bituminous binder material. i

It has been found, however, that the process may be considerably simplified by omitting the addition of the benzol or other solvent material and directly mixing I the bituminous binder and mineral aggregate with the application of moderate heat after first thoroughly drying the mineral aggregate and removing the volatile hydrocarbons from the bituminous material. If all of the moisture is removed from the sand, crushed stone or mineral aggregate, it is possible to make a satisfactory mix of the bitumen and mineral aggregate. I

Since the bituminous binder material used in the manufacture of the surfacing material has some precentage of the lighter petroleum hydrocarbons remaining in it after the bulk of the petroleum has been removed, either through distillation or. otherwise, it is necessary in order to form a surfacing material having lastingand enduring qualities that all or substantially all of these lighter petroleum hydrocarbons, such as gasolene or the-like,'be'

surfacing material to be made by the present process will contain an exceptionally large proportion of heavier petroleum oils in order to increase its-plasticityand resiliency, but

in orderto prevent early deterioration 'ofthe final material it is necessary to remove practically allof the lighterhydrocarbons which are mingled with the heavier oils and which remain in combinationtherewith after the ordinary topping or fractional distillation methods have been used. a

According to "the present invention it is proposed to first treat the bituminous binder material, which comprises bitumenor asphalt combined'with crude petroleum or pe troleum residues, to remove substantially completely the lighter and more volatile hydrocarbons which may be present therein by subjecting the material to a'temperature of from 150 to 275,degrees F. while under a vacuum of from 21 to 28'inches. This treatment results in a substantially complete re-- moval of the lighter hydrocarbons without removing the heavier oils and without causing deterioration of the lubricating, qualities of the heavier hydrocarbon constituents by subjecting them to excessive heating. The mineral aggregate is then heated to completely drive oil anyv moisture therein contained and is then mixed with the 'previ-' ously treated. bituminous binder material. This mixing may be 'efl'ected when both the mineral aggregate and the bituminous binder material are in a heated condition in order that the binder material may be able better. to penetrate into the interstices in the mineral aggregate and thoroughly coat all sides of each mineral particle. The materials may also be subjectedto moderate heat during the mixing operation in order to secure a more complete and thorough mixing so that each mineral particle is completely coated with the bitumen. a

In mixing the bituminous binder, and mineral aggregate, it is regarded as prefer able that the mineral aggregate be first heated to a temperature of approximately 300 'to 400 degrees F. to remove the moisture there-' from and then 'be immediately combined with the bituminous binder material which has also been heated to a temperature ofabout 150 to 200 degrees F. If desired moderate heat may be applied to the mixing receptacle to maintain the temperature of the mass at approximately 150 to 275 degrees F. during the mixing operation. During themixing operation the materials are agitated C011. tinuously to thoroughly combine the mineral aggregate withthe bituminous binder and insure complete amalgamation of the constituents as well as a thorough coating of each mineralparticle with the bituminous V binder material. 1

- The mixing of the bituminous binder and a compact mass. The discharged material may be subjected to a current of cool air instead of being discharged into water and may be agitated by stirrers or in any other 1 desired manner during the cooling operation,

as by being allowed to fall from a considerable height, to break up the lumps of material; orv any suitable combination of water cooling and: air cooling means may be.em-

ployed preferably in combination with some method of agitating the material, during the cooling operation. The agitation of the. combined materials in the mixing chamber will in each case be made sufiiciently complete to thoroughly coat each particle of the mineral aggregate with the bituminous binder material and will at the same time cause such agitation of the mass as will prevent undue cohesion of the particles. 7

It has been found that by first removing the more volatile hydrocarbon constituents from the petroleum component of the bituminous binder material, and by preheating the bituminous bindermaterial and mineral aggregate prior to mixing the same together, the amalgamation of these elements may be readily effected in an open chamber and the trouble and expense incident to the addition of asolvent liquid to and its subsequent removal from the bituminous binder material eliminated.

The paving material thus formed when agitated continuously during the cooling step is of a loose granularcharacter, does not readily pack together and substantially retains its granular character while. being transported to the place-where it is to be used so that it may be easily handled and readily spread upon a road surface. After being spread upon the road surface, pressure is applied by means of a roller, in accordance with thegenera-l practice, which serves to compact together the bitumen coated mineral particles and form afirm surface. The sub stantially' complete removal of the morevolatile hydrocarbon constituents of the petro'leum component of the bituminous binder together with the retention of the heavy lubricating oils, and the fact that the bituminous binder has not been exposed to unduly high temperatures during the heating results in the production of a material which possesses ahigh degree of resiliency and which will not he materiallysoftenedby summerheat .nor'rendered brittle by the cold ofvvinter.

The material is highly resistant to the destructive effects of heavy trafiic and capable of withstanding extremes of temperature. While the main purpose forwhich it is intended to employ the improved surfacing material above described is for use as a surfacing or sub-surfacing for roadways, walks, and the like, it may be used to advantage as an insulating material and in construction work generally where it may be desired to employ an insulating and waterproof material which can be readily handled and compressed by pressure. r

The paving material formed in the manner above described can be laid on concrete, macadam, gravel, or an asphalt sub-surface material, and maybe firmly united with such base material by first applying an asphaltic paintzto the material .to be covered before laying the paving material.

The relative proportionsof bituminous binder and mineral aggregate which have been found best adapted for use in forming the paving material for use as a surfacing for roadways are approximately 7% 0f bituminous binder material and 93% of minera aggregate by weight.

While I have set forth in considerable detail the various steps employed in. the process of making my improved material as well as the proportionate quantities of the constituents Whichhave been found to be best adapted for the production'of an eiiicient material of the characterdescribed, it is to be understood that various changes may be made in the steps of the process and the order in which the various steps are. carried out as well as inthe proportions of'the constituent mate rials employed Without departing from the spirit and scope of myinvention as set forth in the appended claims whichare to be broadly construed in the light of my disclosure. What I claim is i 1. In the process of making a surfacing '1" material formed by combining a mineral aggregate with a bituminous binder material. consisting, of crude petroleum and bitumenv inwhich the crude petroleum content constitutes from 8% to 25% of the bitumen by weight, the step of heating a mixture of crude petroleum and bitumen under a vacuum of from 21 to 28 inches and at a temperature of approximately -200 degrees F. to remove substantially entirely the more volatile hydrocarbon constituents from the-petroleum content of the binder material prior to the mixing of the mineral aggregate with the bituminous binder material.

2. The process of making a surfacing material which comprises, treating a bituminous binder material comprising a mixture of crudepetroleum and bitumen, wherein the crude petroleum content of the mixture constitutes from, 8% to 25% of the bitumen signature.

JOHN W. CLARK. 

